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Purpose The intra‐operative femorotibial joint gap and ligament balance, the predictors affecting these gaps and their balances, as well as the postoperative knee flexion, were examined. These factors were assessed radiographically after a posterior cruciate‐retaining total knee arthroplasty (TKA). The posterior condylar offset and posterior tibial slope have been reported as the most important intra‐operative factors affecting cruciate‐retaining‐type TKAs. The joint gap and balance have not been investigated in assessments of the posterior condylar offset and the posterior tibial slope. Methods The femorotibial gap and medial/lateral ligament balance were measured with an offset‐type tensor. The femorotibial gaps were measured at 0°, 45°, 90° and 135° of knee flexion, and various gap changes were calculated at 0°–90° and 0°–135°. Cruciate‐retaining‐type arthroplasties were performed in 98 knees with varus osteoarthritis. Results The 0°–90° femorotibial gap change was strongly affected by the posterior condylar offset value (postoperative posterior condylar offset subtracted by the preoperative posterior condylar offset). The 0°–135° femorotibial gap change was significantly correlated with the posterior tibial slope and the 135° medial/lateral ligament balance. The postoperative flexion angle was positively correlated with the preoperative flexion angle, γ angle and the posterior tibial slope. Multiple‐regression analysis demonstrated that the preoperative flexion angle, γ angle, posterior tibial slope and 90° medial/lateral ligament balance were significant independent factors for the postoperative knee flexion angle. The flexion angle change (postoperative flexion angle subtracted by the preoperative flexion angle) was also strongly correlated with the preoperative flexion angle, posterior tibial slope and 90° medial/lateral ligament balance. Conclusion The postoperative flexion angle is affected by multiple factors, especially in cruciate‐retaining‐type TKAs. However, it is important to pay attention not only to the posterior tibial slope, but also to the flexion medial/lateral ligament balance during surgery. A cruciate‐retaining‐type TKA has the potential to achieve both stability and a wide range of motion and to improve the patients’ activities of daily living.

Level IV, therapeutic case series.

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Purpose To investigate factors that inluence the prevalence of articular cartilage injury in patients with anterior cruciate ligament (ACL) injury. Methods This multicentre study included patients with ACL injury. Logistic regression analysis was conducted to identify factors that inluence the prevalence of cartilage injury during ACL reconstruction. Results A total of 811 patients were enrolled. The factors that signiicantly inluenced the prevalence of cartilage injury were age (odds ratio [OR], 1.04; P = 0.000), a positive pivot shift test result (OR, 1.43; P = 0.021), medial meniscal injury (OR, 2.55; P = 0.000), and delayed surgery (≥ 12 months) (OR, 2.52; P = 0.028) in the medial compartment of the knee; age (OR, 1.05; P = 0.000), subjective grades of apprehension during the pivot shift test (OR, 1.46; P = 0.010), lateral meniscal injury (OR, 1.98; P = 0.003), femoro-tibial angle (FTA) (OR, 0.92; P = 0.006), and delayed surgery (≥ 12 months) (OR, 2.63; P = 0.001) in the lateral compartment; and age (OR, 1.06; P = 0.000), body mass index (OR, 1.07; P = 0.028), a positive pivot shift test result (OR, 1.60; P = 0.018), FTA (OR, 0.90; P = 0.006), and delayed surgery (≥ 12 months) (OR, 3.17; P = 0.008) in the patellofemoral compartment. Conclusion An older age, a longer duration between injury and surgery, and a positive pivot shift test result were positively associated with the prevalence of cartilage injury in three compartments in patients with ACL injuries. Early ACL reconstruction is recommended to prevent cartilage injury. Level of Evidence Level III.